1. Field of the Invention
This invention relates to a method for preparing a homogenized mixture of fine powders of heterogeneous substances or of fine powder and a component in the form of whiskers or the like, for use as a starting material in the production of a composite metallic or ceramic material.
2. Description of the Prior Art
In the production of a composite material consisting of two or more heterogeneous substances, it has been the general practice to prepare a mixture of powdery component materials by mechanical mixing. The same method is restored to even when the composite material includes a fibrous component or whiskers.
However, the mechanical mixing of such materials involves the following problems.
In case the components to be mixed are in the form of extremely fine particles, which can be smaller than 0.1 .mu.m in diameter in some cases, it takes a very long time to mix them uniformly due to coagulation of fine particles which makes the mixing difficult. The uniform mixing becomes more difficult when one component is in the form of fibre or whiskers which are easily entangled with each other.
Consequently, the resulting composite material contains local irregularities in strength and properties, failing to make the most of the advantages which would accrue from the use of fine powder or fibre or whiskers.
Further, ultra-fine powder or ultra-fine whiskers which are generally susceptible to oxidation or other chemical reactions, giving rise to various problems or inconveniences in handling, for example, storage or mixing in vacuum or in an inert gas.